The tyrosine-protein kinase transmembrane receptor ROR1 is a cell surface receptor that belongs to the ROR subfamily of cell surface proteins. It shows strong homology to the tyrosine kinase domain of growth factor receptors, in particular the Trk family [Reddy et al. (1997) Genomics 41(2):283-5] and modulates neurite growth in the central nervous system. So far two isoforms have been reported (SWISS-PROT entry; Q01973) and the nucleotide sequence encoding this protein is found at accession number NM—005012.
According to SWISS-PROT, the tyrosine-protein kinase transmembrane receptor ROR1 is expressed strongly in human heart, lung, and kidney, but weakly in the CNS. The short isoform (missing amino acids 1-549 of the long isoform) is strongly expressed in fetal and adult CNS and in a variety of human cancers, including those originating from CNS or PNS neuroectoderm. The tyrosine-protein kinase transmembrane receptor ROR1 (described as ROR1 henceforward) is expressed at high levels during early embryonic development. The expression levels drop strongly around day 16 and there are only very low levels in adult tissues. Over-expression of the ROR1 gene has recently been reported in B-cell chronic lymphocytic leukemia [Basker et al. (2008) Clin Cancer Res. 14(2):396-404].